Abstract

Background:

Sarcomas are characterized by significant heterogeneity, diverse histological subtypes, and variable clinical behavior. Dynamic epithelial-to-mesenchymal transition (EMT) processes in solid tumors contribute to disease aggressiveness. Characterization of circulating tumor cells (CTCs) in sarcomas remains challenging due to the lack of well-defined, cell-specific markers and limited molecular characterization. Compared with adenocarcinomas, studies on sarcoma-derived CTCs are relatively limited. Therefore, isolation and characterization of CTCs, including assessment of protein expression and cellular transitions using affinity ligands such as anti-epithelial cell adhesion molecule (EpCAM) antibodies, may improve clinical outcomes in sarcoma patients. The role of CTCs as minimal cellular residual disease (MCRD) is particularly relevant post-treatment, including after curative-intent surgery.

Objective:

To evaluate the prevalence of CTCs and CTC clusters as indicators of minimal cellular residual disease (MCRD), along with PD-L1 expression, in sarcoma patients.

Methods:

In this retrospective study, peripheral blood samples from 97 sarcoma patients (55.95% male and 44.05% female) were analyzed for the presence of CTCs, PD-L1 expression, and CTC clusters. CTCs were isolated using the OncoDiscover platform approved by CDSCO from 1.5 mL of blood. The platform utilizes a multifunctional magneto-nanosystem mediated by anti-EpCAM antibodies. CTCs were identified as EpCAM⁺, CK18⁺, DAPI⁺, and CD45⁻ cells. PD-L1 expression on CTCs was quantified based on linear fluorescence intensity gradients using image acquisition on an automated Zeiss microscope.

Results:

Among the 97 patients, 86.59% had baseline CTC assessments, while 13.40% had follow-up samples. At baseline analysis, 68.04% (n = 66) of patients demonstrated ≥1 CTC per 1.5 mL of blood. The CTC count ranged from 1 to 6 cells, with a mean value of 1.17. Additionally, 61.44% (n = 51) of patients with detectable CTCs exhibited PD-L1 expression, with a mean value of 0.92. The highest proportion of CTCs (31.11%, n = 28) and CTC clusters (6.14%, n = 7) was observed in the 31–40-year age group.

Conclusions:

The presence of CTCs with CTC clusters and PD-L1 expression suggests minimal cellular residual disease (MCRD) and may indicate aggressive disease behavior in sarcoma patients. Following treatment, the detection of such CTCs may be associated with metastasis progression. Therefore, longitudinal monitoring of these patients is recommended to support improved clinical outcomes.